As is well known, a printed circuit board comprises a support structure formed from an electrically insulative material having formed on at least one side thereof a series of electrically conductive paths or leads. Typically, a plurality of apertures are formed through the board, and components such as resistors, capacitors, transistors, integrated circuits, etc. are mounted on the board by the insertion of electrically conductive pins extending from each component through the apertures. Solder connections are then formed between the conductive pins of the components and the conductive leads of the printed circuit board, thereby completing the necessary electrical connections between the various components.
As will be readily apparent, when a particular printed circuit board requires the replacement, addition, removal and/or testing of numerous components, many opportunities exist for operator error. For example, many types of components are almost identical in appearance, but widely differ in function. When the design of a particular printed circuit board requires the positioning of different types of components in relatively adjacent locations, the mounting or testing of components in incorrect locations or the removal of components from incorrect locations can usually occur. In addition, integrated circuits and other components often have a particular polarity. Even when the conductive pins of such a component are positioned in a correct aperture, the orientation of the component may be reversed, which means that the polarity of the component is incorrect. It will be understood that if the conductive pins of a particular component are positioned in the wrong apertures or if a component is mounted in the wrong orientation, and if such errors are not detected until after the completion of subsequent steps in the printed circuit board operation, costly and time consuming rework procedures may be necessary in order to salvage the printed circuit board. In some cases the extent of these procedures may be such that it is impractical to attempt salvage, whereupon the board must be scrapped. Similarly, costly and time consuming rework procedures may be caused unnecessarily by mistakenly testing the wrong component of a printed circuit board since the tested component would likely be a different type than the intended component and therefore incorrectly identified as being defective.
A related problem involves the fact that it is often necessary to assemble, modify, repair and/or test a complex printed circuit board in accordance with a predetermined schedule. Unless the schedule is strictly adhered to it may be difficult or impossible to carry out subsequent steps in any associated process. Here again, any deviation from the correct schedule may require costly and time consuming rework procedures.
Recognition of the foregoing problems has led to prior attempts at automating the assembly, modification, repair and/or testing of printed circuit boards. For example, one prior system includes structure for projecting a beam of light at the particular set of apertures which are to receive the next component of the printed circuit board. Such a system may be utilized in conjunction with a previously prepared component list, so that the operator can select components in sequence from the list and then insert each component at the location indicated by the projected light beam. Although such a system is certainly preferable to no system at all, various deficiencies with respect to the full automation of printed circuit board assembly remain. For example, a projected light beam type system does not include any procedure for guiding the operator with respect to component orientation, so that even though the correct component is positioned in the correct apertures its polarity may be reversed. Also, it is entirely conceivable that the operator would skip ahead or fall behind relative to the list, leading to the insertion of an incorrect component in the apertures indicated by the projected light beam.
As is well known in the industry, engineering change notices are frequently issued regarding previously manufactured printed circuit boards. For example, a particular printed circuit board model may incorporate design deficiency, or it may become desirable to rework a printed circuit board model to accommodate changing circumstances or to facilitate the performance of new or revised functions. Heretofore, no system has been provided for automating the reworking of printed circuit boards in accordance with engineering change notices.
Another well known deficiency has to do with the repair of defective printed circuit boards. At the present time there does not exist a commercially practical system for automating the repair of defective printed circuit boards and the associated testing of the boards prior to or following repair.
The present invention comprises a system for manufacturing, changing, repairing and/or testing printed circuit boards which overcomes the foregoing and other problems long since associated with the prior art. In accordance with certain aspects of the invention, each step of operations to be performed on a printed circuit board is characterized by the projection of a full color image of the component to be inserted, replaced, removed and/or tested at the precise location on the printed circuit board at which the component is situated or the repair opertion is to take place. Each step of a procedure is also characterized by verbal instructions to the operator relating to a particular component and the operation to be performed thereon or to a particular repair operation and the location thereof. Any step in the procedure may include a visual indication to the operator as to the particular component to be selected from a component storage array. Thus, at each step in the printed circuit board assembly, repair, modification and/or testing process the operator is visually and verbally instructed as to which component to mount, remove or test, and is then visually and verbally instructed as to the location of the component on the printed circuit board and as to the proper orientation of the component if necessary.
In accordance with yet another aspect of the invention, the step by step process of inserting, removing and/or testing components is periodically interrupted for a review of the previously accomplished steps. For example, assume that the assembly procedure has progressed to the point that all of the integrated circuits should be in place. At this time an image can be projected onto the printed circuit board showing the entire array of integrated circuits which are to comprise the completed printed circuit board, including the proper location and orientation of each integrated circuit. At this time the operator can also receive verbal instructions as to the proper number of integrated circuits, and as to the proper location and orientation of each. This allows any previous error as to component selection, positioning or orientation to be immediately corrected in advance of subsequent assembly steps which might significantly complicate the correction process. A similar procedure may also be incorporated with modification, repair, or testing operations.
In accordance with more specific aspects of the invention, a printed circuit board assembly system includes a work station adapted to properly position a printed circuit board for the assembly of components therein. All of the components necessary for the assembly of a particular printed circuit board are arranged in a predetermined component array situated immediately adjacent the work station. Structure is provided for projecting component images, either directly onto the printed circuit board or onto a display screen oriented to facilitate comparison of the image on the screen with the component being inserted into the printed circuit board. Structure is also provided for verbally instructing the operator as to each step of the assembly procedure, and as to the precise location of the next component to be selected from the component array.
The invention further comprises a system for automating the implementation of engineering change notices pertaining to printed circuit boards. In a typical case, a series of visual images and a corresponding series of verbal instructions are first generated to facilitate the cutting of one or more electrically conductive leads or paths previously formed on the etched face or underside of the circuit board. Next, a series of visual images and a corresponding series of verbal instructions are generated with respect to the information of new conducting paths between predetermined points on the printed circuit board. The new circuit paths may comprise lengths of insulated wire extending either point-to-point or in accordance with predetermined coordinates and are adhesively secured in place.
Still another aspect of the invention involves the testing and repair of defective printed circuit boards. If the defect is not known, the system of the present invention may be utilized to conduct a series of tests for the purpose of identifying the component or components that are causing the defect. Then, the system is utilized in a manner similar to that described above in conjunction with the manufacture of printed circuit boards to facilitate the removal and replacement of the defective component or components. Finally, the system is used to test the repaired printed circuit board to be sure that all of the defects therein have been corrected.